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35 lines
1.7 KiB
Diff
35 lines
1.7 KiB
Diff
From afd6952c4dfb0d4945b496ef08b2f478d6f40097 Mon Sep 17 00:00:00 2001
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From: Jacopo Mondi <jacopo@jmondi.org>
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Date: Tue, 7 Apr 2020 17:21:55 +0200
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Subject: [PATCH] Documentation: media: Update sub-device API intro
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Update the V4L2 sub-device userspace API introduction to provide more
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details on why complex devices might want to register devnodes for the
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connected subdevices.
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Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
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Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
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---
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Documentation/media/kapi/v4l2-subdev.rst | 9 +++++++--
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1 file changed, 7 insertions(+), 2 deletions(-)
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--- a/Documentation/media/kapi/v4l2-subdev.rst
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+++ b/Documentation/media/kapi/v4l2-subdev.rst
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@@ -275,8 +275,13 @@ system the .unbind() method is called. A
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V4L2 sub-device userspace API
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-----------------------------
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-Beside exposing a kernel API through the :c:type:`v4l2_subdev_ops` structure,
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-V4L2 sub-devices can also be controlled directly by userspace applications.
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+Bridge drivers traditionally expose one or multiple video nodes to userspace,
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+and control subdevices through the :c:type:`v4l2_subdev_ops` operations in
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+response to video node operations. This hides the complexity of the underlying
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+hardware from applications. For complex devices, finer-grained control of the
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+device than what the video nodes offer may be required. In those cases, bridge
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+drivers that implement :ref:`the media controller API <media_controller>` may
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+opt for making the subdevice operations directly accessible from userpace.
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Device nodes named ``v4l-subdev``\ *X* can be created in ``/dev`` to access
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sub-devices directly. If a sub-device supports direct userspace configuration
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